GMAT数学备考资料：费费数学宝典详解版(九)
<p> 11、<span word="S">S</span>=<span word="m">m</span> <span word="and">and</span> <span word="m">m</span> <span word="is">is</span> <span word="a">a</span> <span word="positive">positive</span> <span word="integer">integer</span>. <span word="Which">Which</span> <span word="of">of</span> <span word="the">the</span> <span word="following">following</span> <span word="must">must</span> <span word="be">be</span> <span word="true">true</span>?</p><p> <span word="S">S</span> <span word="is">is</span> <span word="divisible">divisible</span> <span word="by">by</span> 3</p><p> <span word="S">S</span> <span word="is">is</span> <span word="divisible">divisible</span> <span word="by">by</span> 4</p><p> <span word="S">S</span> <span word="is">is</span> <span word="divisible">divisible</span> <span word="by">by</span> 6</p><p> 【答案】1 <span word="AND">AND</span> 3</p><p> 【思路】连续的三个自然数既可以被2整除，也可被3整除，则可被6整除。而<span word="M">M</span>与刚好相差3，也就是<span word="M">M</span>+3值的特征与<span word="M">M</span>值的特征是一样的，则<span word="S">S</span>可以看成连续的三个自然数</p><p> 12、一个经理在12个时间段中任选7个，<span word="interview">interview</span>7个申请人，问：有几种方法?</p><p> 【答案】<span word="P">P</span></p><p> 【思路】从12个时间段中选7个，与7个申请人进行全排列。</p><p> 或者第一个可从12个时间段中选一个，依次，第二个可从11个中选一个。。。等等，总共有1211109876中方法。</p><p> 13、<span word="f">f</span>=2^<span word="x">x</span>3^<span word="y">y</span>5^<span word="z">z</span>，<span word="x">x</span>, <span word="y">y</span>, <span word="z">z</span>分别是整数<span word="n">n</span>的百位、十位和个位。<span word="f">f</span>=9<span word="f">f</span>，<span word="m">m</span>-<span word="h">h</span>=?</p><p> 【答案】20</p><p> 【思路】<span word="f">f</span>=9<span word="f">f</span>=3^2 <span word="f">f</span>，根据题目可知3^2是<span word="Y">Y</span>的指数相差2，而<span word="X">X</span>、<span word="Z">Z</span>是相同的，又<span word="Y">Y</span>是整数的十位。则<span word="f">f</span> 比<span word="f">f</span>2个十位，也就是20</p><p> 14、<span word="For">For</span> <span word="all">all</span> <span word="x">x</span>, <span word="x">x</span>^2+6<span word="x">x</span>+<span word="q">q</span>，<span word="q">q</span>为常数，问<span word="q">q</span>=?</p><p> ^2+4=<span word="x">x</span>^2+6<span word="x">x</span>+<span word="q">q</span></p><p> =<span word="x">x</span>^2+6<span word="x">x</span>+<span word="q">q</span></p><p> 【答案】<span word="A">A</span></p><p> 【思路】^2+4=<span word="x">x</span>^2+6<span word="x">x</span>+<span word="q">q</span>= <span word="x">x</span>^2+2<span word="rx">rx</span>+<span word="r">r</span>^2+4则2<span word="r">r</span>=6 <span word="r">r</span>和^2+4=<span word="q">q</span> 因此<span word="r">r</span>=3 <span word="q">q</span>=13 分页标题#<span word="e">e</span>#</p>
页:
[1]